I’ve used the ones from betterscanning.com, and they work well. I tried the ones from Scan Tech for my Epson V850 (120), and despite the site saying it would work, they didn’t. I got a refund. I think the V850 holders are very different from previous Epson models in that they load “upside down” and the glass would fall out if you inverted the holders for scanning position.
Prior to using my Fuji X-H1 for scanning my negatives, I had been using an Epson v550. I bought a 2-pack of Scan Tech ANR glass inserts for the Epson 35mm holder and a single 120 ANR glass insert for the medium format film holder. I think they worked wonderfully for reducing glare, eliminating newton rings, and for keeping the film flat. Now that I have started scanning with a mirrorless camera, I am still using my Epson film holders with the ANR glass inserts on top of my light pad. The film holders keep the film slightly above the light pad and the ANR glass keeps reflections down too. I think the Scan Tech glass is a good investment, especially if you already have Epson holders.
I ordered two x 120 holders which I imagine will give me leverage with 35mm film as well. Just hope they actually send them as ordering goes straight to PayPal and there was zero correspondence from the company.
I’m using my X-T30 with a 60macro and so far so good but would really like to flatten my negs more as several are super curled.
They arrived last week but I haven’t had a chance to use them. Shooting my rolls of film as contact sheets first. Shoulda got a 9x12” glass as well to keep a while roll flat!
I’ll update once I use them.
I’m in a similar situation. I have been using a V600 for my 6x7/6x6 negs but only recently started doing dslr scanning with digitaliza+kaiser slimlite. It’s fast and gets me decent results but the digitaliza can’t keep the negs perfectly flat, especially the frame in the middle of the holder. Now I’m also thinking about getting ANR glasses to have the negs sandwiched in between. Please keep us updated with your experiments, thanks!